1. Field of the Invention
The invention relates to a device (an apparatus) for increasing the temperature of elongate metallic rolled stock, having a heating unit which comprises induction heating elements for heating the rolled stock along a heating zone and having a conveying device which comprises driving and/or roller table roller elements as active or passive conveying elements for moving the rolled stock along the longitudinal extension of the heating zone, the induction heating elements being arranged spaced apart from one other in the longitudinal extension of the heating zone in each case by a free space.
The invention further relates to a finishing train for producing and/or working elongate metallic rolled stock, having an apparatus for increasing the temperature of the elongate metallic rolled stock.
2. Description of Related Art
Generic apparatuses for heating elongate metallic rolled stock, such as strips, slabs or the like, in a desired manner are well known in the prior art. In these apparatuses, the elongate metallic rolled stock must frequently be guided past a series of induction heating elements that have an induction heating element clearance height which is designed to be relatively narrow so that the rolled stock can be guided as close as possible past the induction heating elements, thereby allowing maximum efficiency with respect to the heating unit to be achieved. This is particularly the case when thinner strips 8 mm to 30 mm in thickness, for example, are to be heated by means of a longitudinal field induction heating element. It is known that upstream of a corresponding induction heating element zone, or heating zone—as viewed in the direction of conveyance—any irregularities, bulges and/or strip skis with respect to the elongate metallic rolled stock can be reduced, for example, using a strip straightener or a leveler and/or by means of a crop cut at the strip head. Depending on the prevailing constraints of the respective apparatus, however, bulges, strip skis or the like may still be present. Furthermore, bulging of the elongate metallic rolled stock may change or even increase over a longer induction heating element zone, for example 3 m in length, for example due to uneven heating or asymmetrical temperature losses from the top to the bottom side of the elongate metallic rolled stock. Moreover, in the case of a failure of units downstream, disruptions in material flow, a power failure during conveyance of the rolled stock, etc., a strip loop may form in the region of the induction heating element zone.
These effects, described merely by way of example, can cause the elongate metallic rolled stock to come into contact with one or more of the induction heating elements, resulting in permanent damage to the heating unit.
To reduce the risk of contact between the elongate metallic rolled stock and the induction heating elements within an induction heating element zone, document CA 2 633 942 C discloses an apparatus comprising a strip edge heater with induction heating elements, which are arranged on either side of a central longitudinal axis of a heating zone of the apparatus. Both upstream and downstream of the induction heating elements, components of a leveler are positioned for leveling the rolled stock. These components are additionally connected to one another via an elongate center component of the leveler, so that the leveler extends in its entirety continuously along the induction heating element zone from an intake region upstream of the induction heating element zone up to an output region downstream of the induction heating element zone. With this leveler configuration, the rolled stock can continue to be leveled during the heating of its edge regions. However, the continuous configuration of the leveler makes the apparatus quite large. In addition, particularly with thinner rolled stock, such as thinner strips or the like, the leveler thus configured cannot positively prevent lateral regions of the thinner rolled stock from coming into contact with the induction heating elements when corresponding deformation occurs despite the center component. In this respect, the apparatus described in the cited document is in no way suitable for increasing the temperature of thinner rolled stock by means of longitudinal field induction. Furthermore, this leveler has an adverse effect on the heating of the rolled stock because the elongate center component is arranged at the center of the heating zone. This center component is therefore also disadvantageously exposed to tremendous heat. Moreover, due to the positioning of the elongate center component of the leveler, this configuration is suitable only for use in conjunction with a strip edge heating system. And the leveler known from document CA 2 633 942 C cannot even be used with induction heating elements that are arranged continuously from one side to the other side.
Further, from Japanese abstract JP 11 123 438 A another hot rolling mill is known, which has an induction heating unit having a plurality of induction heating coils for heating elongate metallic rolled stock. In this case, the elongate metallic rolled stock is conveyed in the direction of transport through the respective induction heating coil gap. To eliminate the risk of the elongate metallic rolled stock inadvertently colliding with the inner sides of the induction heating coils, two or more tubular elements are disposed between each of the induction heating coils and both the upper side and the underside of the elongate metallic rolled stock. The tubular elements disposed on the upper side and the underside of the elongate metallic rolled stock in each induction heating coil extend with their longitudinal extension in the direction of transport of the elongate metallic rolled stock, and are arranged side by side and spaced from one another transversely to the direction of transport. The tubular elements in this case are bent in a U-shape with the ends thereof facing away from the respective induction heating coil. Coolant connections are provided at the ends, since a coolant flows through the tubular elements to cool them. This is essential because the tubular elements are positioned in the region of the induction field between the inner sides of the induction heating coils and the elongate metallic rolled stock. They are thus exposed directly to a corresponding heat load. A further disadvantage is that this configuration also adversely affects the heating output of the induction device. In addition, the tubular elements further constrict the inductor passage dimensions.
The object of the invention is to further develop apparatuses for heating elongate metallic rolled stock, in particular thinner metallic strips such as thin steel strips, such that the risk of contact with and possible damage particularly to induction heating elements by elongate metallic rolled stock can be extensively avoided.